1. Field of the Invention
This invention relates to an image recording system, and particularly, to a system including a solid state image transducer provided with a large number of independent photoelectric elements independent, image forming optics for forming an image of an object on the image transducer, and a recording medium on which the image signals for the object image obtained from the solid state image transducer are reproducibly accumulated.
2. Description of the Prior Art
The television art, especially color television art employs so-called charge transfer devices, such as CCD and BBD devices, as image sensors, for example, as shown in U.S. Pat. No. 3,982,274. Also known is a method and apparatus for recording and reproducing still pictures by processing the output of such devices so that the image signals, after having been stored, are read out at a relatively slow speed and then converted to video signals which are to be recorded on a magnetic recording medium such as a magnetic disc, as, for example, disclosed in U.S. Pat. No. 4,057,830.
These prior art systems, however, are concerned only with the function of recording the image signals on the magnetic recording medium, and disclose nothing about an exposure level control in producing the image signals. For this reason, the prior art system tends to record some of the image signals in an over-exposed condition, and some in an under-exposed condition, so that a reliable image of optimum tone-reproduction quality cannot be obtained.
For a solid state image transducer, it is desirable to use a charge transfer type device such as CCD and BBD, or X-Y address type device, or a charge injection type device (CID). These devices are fabricated in the form of integrated circuits on a thin silicon semi-conductor substrate. Thus, when the image-receiving surface of the solid state device is accidentally exposed through the image forming optical system to a very intense radiant energy particularly from the sun, there is a great possibility of suddenly heating a portion of the exposed surface of the device to so high a temperature that the solid state device is damaged. Another disadvantage of the prior art systems is that the recorded image is monitored by an optical finder similar to that in the conventional photographic camera.
The prominent advantage of such an electronic image recording system over a photographic camera using conventional photosensitive materials of the silver halide type is, however, the possibility of instant reproduction of recorded image signals by means, for example, of a television set.